1. Field of the Invention
The present invention relates to a measurement system of a three-dimensional shape of an optical component and the like, a measuring method thereof, and a computer program product.
2. Description of Related Art
In manufacture of a micro electrical machine system (MEMS) apparatus, a semiconductor device and the like, a pattern of an exposure mask or an imprint mold is transferred onto a substrate to be processed using a lithography process, such as a photolithography, an imprint lithograph, and the like. In association with miniaturization of the transferred pattern, a shape of the exposure mask or the imprint mold has an influence on accuracy of position or dimension of the transferred pattern. In order to control the shape of the exposure mask or the imprint mold, a shape measurement may be required.
For example, in a transmission exposure mask, a flatness of a surface of the exposure mask, on which the mask pattern is formed, is usually the most critical item, and a strict specification is defined. With regard to measurement of the flatness of the exposure mask, various efforts are carried out (refer to JP-A Hei4-133061 (KOKAI)). Shape factors, such as a dimension and the like, except the flatness, may be relatively less important, and may not measure with high accuracy. Also, for measurement values of the shape obtained from a plurality of measuring methods, consistency between the respective measurement values of the shape is not considered.
However, in association with improvement of optical systems of exposure tools, an outer shape, especially, a position relation between surfaces is required to strictly define. For example, in an exposure mask for extreme ultraviolet (EUV) light, the strict specification must be defined not only for the flatness of the surface, on which the mask pattern is formed, but also for the other shape factors.
In the EUV exposure, a reflection optical system is used. In this case, the exposure mask is supported by fixing a bottom surface of the exposure mask on a mask stage. Therefore, when a parallelism between top and bottom surfaces of the exposure mask is large, it is difficult to achieve the intended reflection angle for an exposure light. Thus, it is necessary to strictly define the parallelism between the top surface and the bottom surface of the exposure mask. Moreover, since there is a requirement to precisely identify the position of the mask pattern to a mask substrate of the exposure mask, accuracy of the outside dimensions of the mask substrate may be also required.
In the imprint lithography, the imprint mold is pressed into a transfer film, and then a minute concave and convex pattern formed on the surface of the imprint mold is transferred. As a method for carrying out a distortion correction for the transferred pattern, a method, which carries out the correction by applying an external force to the imprint mold and consequently generating minute deformation, is proposed (refer to JP-A 2006-510223(KOKAI), and J. Choi et al., MNE Micro- and Nano-Engineering Conference, 2004, September).
In order to achieve the foregoing distortion compensation in the imprint lithography, the imprint mold must be manufactured to have the ideal rectangular parallelepiped defined in the specification. Unless the imprint mold has the outer shape defined in the specification, it is difficult to deform the imprint mold to the intended shape by using the external force, and a result obtained by transfer cannot be desirable.
In the usual shape measurement, for example, dimensions, angles, flatness and the like are individually measured by respective measurement systems differing from each other. For this reason, when the respective measurement values are substituted to simulate the shape, there might be no consistency between the respective measurement values so that a figure is not geometrically formed. Also, when the specification of the shape is close to limits of the measurement accuracy of the measurement systems, a range of error of each measurement value increases. As a result, since calculated values by simulation of the shape may have a wide range, the simulation result may have lower reliability. Also, since a calculation amount is increased, a measuring time may be increased, and productivity of the imprint mold or the exposure mask may be decreased.